Select sister elements of a table in jquery

I want to fill a td element by accessing other td s in the same row. How would I access them using jQuery?

In my situation, I have a table, and column 5 is populated by subtracting col 3 from col 4, and returning the result in col 5. I started to do it with a nested loop, but realized, that if I used the .each() on each col 5 td, it would be achievable if I could identify col 3 and 4 using jQuery.

You can select one element (table cell in your case), and then use jQuery.prev() or jQuery.next() to select previous or next sibling element. In native DOM, you could use previousSibling/nextSibling (or previousElementSibling/nextElementSibling in modern browsers to skip non-element nodes) element properties for same purpose.